A bullet 2cm log is fired at 420m/s and passes straight a 10cm thick board exiting at 280m/s

Complete question:

A bullet 2 cm long is fired at 420m/s and passes straight through a 10.0 cm thick board, exiting at 280m/s? What is the average acceleration of the bullet through the board?

The average acceleration of the bullet through the board is -4.083 x 10⁵ m/s²

Explanation:

Given;

initial velocity of the bullet, u = 420 m/s

final velocity of the bullet, v = 280 m/s

length of the bullet, d₁ = 2 cm

thickness of the board, d₂ = 10 cm

total distance penetrated by the bullet through the board;

d = d₁ + d₂ = 2 cm + 10 cm = 12 cm = 0.12 m

The average acceleration of the bullet through the board is calculated as;

Therefore, the average acceleration of the bullet through the board is -4.083 x 10⁵ m/s²

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.